Some research suggests that your body's natural fight-or-flight response to danger is involved in panic attacks. For example, if a grizzly bear came after you, your body would react instinctively. Your heart rate and breathing would speed up as your body prepared for a life-threatening situation. Many of the same reactions occur in a panic attack. But it's unknown why a panic attack occurs when there's no obvious danger present.
Panic disorder involves repeated episodes of sudden feelings of intense anxiety and fear or terror that reach a peak within minutes (panic attacks). You may have feelings of impending doom, shortness of breath, chest pain, or a rapid, fluttering or pounding heart (heart palpitations). These panic attacks may lead to worrying about them happening again or avoiding situations in which they've occurred.

Says Clyman: "You might start to consider your emotions as changing experiences that are always fluctuating. When we feel distressed, it can seem like the distress is going to go on and on forever until we emotionally combust. But instead, emotions act more like a wave, at times increasing and becoming more intense. But inevitably they'll reach a plateau, subsiding and finally passing."

Occasional anxiety is an expected part of life. You might feel anxious when faced with a problem at work, before taking a test, or before making an important decision. But anxiety disorders involve more than temporary worry or fear. For a person with an anxiety disorder, the anxiety does not go away and can get worse over time. The symptoms can interfere with daily activities such as job performance, school work, and relationships.